Hi Chi,
Make Sure you have Expressway-C and E configured with "Unified Communications traversal zone" instead of using the regular Traversal Server/Client zone.
Please check login issues discussed in below URL:
https://www.cisco.com/c/en/us/support/docs/unified-communications/expressway/118798-technote-cucm-00.html#anc11
Also, what authentication error messages do you see under Expressway Event Logs?
Thanks,
VS
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Thanks, Vaijanath S.